The Design And Construction Of A 35 Watt Audio Amplifier With Dual Power Supply

ABSTRACT

This work is titled the design and construction of a 35 Watt Amplifier. An audio Amplifier is a device for increasing the audio power of a signal by use of an external energy source. It is design to meet up with the amplification demand in homes, offices, industries and especially in music industries. An audio Amplifier low-power audio signals (signals composed primarily of frequencies between 20 – 20 000 Hz, the human range of hearing) to a level suitable for driving loudspeakers and is the final stage in a typical audio playback chain, While the input signal to an audio amplifier may measure only a few hundred microwatts, its output may be tens, hundreds, or thousands of watts.

This device is designed to deliver appreciable 35 Watt power to the load which is run from a 12v mains power supply and rechargeable battery. The 12v rechargeable battery used in this work functions as a standby power supply which comes to work whenever the mains power fails.

TABLE OF CONTENTS

Title Page

Approval Page

Dedication

Acknowledgement

Abstract

Table of Content

CHAPTER ONE

1.0      Introduction

1.1      Objective of the project

1.3     Application of the project

1.4      purpose of the project

1.5      significance of the project

1.6      limitation of the project

1.7      project organization

CHAPTER TWO

2.0     Literature review

2.1      Historitical background of an amplifier

2.2   Review of classification of power amplifiers

2.3      Classification according to mode of operation

2.4       Review of transistor biasing

CHAPTER THREE

3.0     Construction

3.1      Block diagram of an audio power amplifier

3.2      Circuit diagram of a 35w amplifier

3.3      Circuit operation

3.4     Circuit description

3.5     Power supply circuit

3.6      Parts list of 35 watt amplifier circuit

3.7      Description of components used

CHAPTER FOUR

RESULT ANALYSIS

4.0      Construction Procedure and Testing

4.1      Casing and Packaging

4.2      Assembling of Sections

4.3      Testing of System Operation

4.4      Cost Analysis

CHAPTER FIVE

5.1      Conclusion

5.2      Recommendation

5.3      References

1.0                                                        INTRODUCTION

An audio amplifier is an electronic amplifier that amplifies low-power audio signals (signals composed primarily of frequencies between 20 – 20 000 Hz, the human range of hearing) to a level suitable for driving loudspeakers. It is the final electronic stage in a typical audio playback chain.

Audio stereo power amplifier is design to deliver power to the load (speaker), is the product of the voltage and current applied to the load with the output signal power being greater than the input signal power. In other words, a power amplifier amplifies the power of the input signal which is why these types of amplifier circuits are used in audio amplifier output stages to drive loudspeakers.

The power amplifier works on the basic principle of converting the DC power drawn from the power supply into an AC voltage signal delivered to the load. Although the amplification is high the efficiency of the conversion from the DC power supply input to the AC voltage signal output is usually poor.

The preceding stages in such a chain are low power audio amplifiers which perform tasks like pre-amplification (this is particularly associated with record turntable signals), equalization, tone controls, mixing/effects, or audio sources like record players, CD players, and cassette players. Most audio power amplifiers require these low-level inputs to adhere to line levels.

While the input signal to an audio power amplifier may measure only a few hundred microwatts, its output may be tens or hundreds of watts for a home system or thousands or tens of thousands of watts for a concert sound reinforcement system.

Not all amplifiers are the same and are therefore classified according to their circuit configurations and methods of operation. In “Electronics”, small signal amplifiers are commonly used devices as they have the ability to amplify a relatively small input signal, for example from a Sensor such as a photo-device, into a much larger output signal to drive a relay, lamp or loudspeaker for example.

There are many forms of electronic circuits classed as amplifiers, from Operational Amplifiers and Small Signal Amplifiers up to Large Signal and Power Amplifiers. The classification of an amplifier depends upon the size of the signal, large or small, its physical configuration and how it processes the input signal, which is the relationship between input signal and current flowing in the load.

1.2                                             OBJECTIVE OF THE PROJECT

The main objective of this work is to design and construct an audio power amplifier that will deliver appreciable 35w power to the load. 35W Audio Power amplifiers may be called upon to supply 35w power to a load (speaker) which is powered by rechargeable battery and also with main power supply.

1.3                                         APPLICATION OF THE PROJECT

Important applications include public address systems, theatrical and concert sound reinforcement systems, and domestic systems such as a stereo or home-theatre system. Instrument amplifiers including guitar amplifiers and electric keyboard amplifiers also use audio power amplifiers. In some cases, the power amplifier for an instrument is integrated into a single amplifier “head” which contains a preamplifier, tone controls, and electronic effects. In other cases, musicians may create a setup with separate rack mount preamplifiers, equalizers, and a power amplifier in a separate chassis.

1.3                                         APPLICATION OF THE PROJECT

Important applications include public address systems, theatrical and concert sound reinforcement systems, and domestic systems such as a stereo or home-theatre system. Instrument amplifiers including guitar amplifiers and electric keyboard amplifiers also use audio power amplifiers. In some cases, the power amplifier for an instrument is integrated into a single amplifier “head” which contains a preamplifier, tone controls, and electronic effects. In other cases, musicians may create a setup with separate rack mount preamplifiers, equalizers, and a power amplifier in a separate chassis.

1.4                                              PURPOSE OF THE PROJECT

Amplifier’s main purpose is to take the weak signal and make it strong to drive a speaker. The stereo power amplifiers usually get necessary amplification energy of input signals from the AC supply. Ideally without distortion an amplifier can deliver signal at the output without distortion.

1.5                                         SIGNIFICANCE OF THE PROJECT

Today there are many categories of amplifiers used for multifarious purposes. In simple terms an amplifier picks up a weak signal and converts it into a strong one. It is widely used in several devices to boost electrical signals. Radios, televisions and telephones are a few examples to point out in this regard. There are innumerable other applications of amplifiers and it is not easy to enumerate all of them. Some of the common types of amplifiers are used in electronic gadgets and audio systems. These are also used in musical instruments and guitars.

Running this device from 12v power supply from mains source and also from a 12V battery makes it simple and portable.

1.6                                           LIMITATION OF THE PROJECT

Noise: This device tends to add some random noise to the signals passing through them, hence degrading the SNR (signal to noise ratio). This, in turn, limits the accuracy of any measurement.

Limited output voltage, current, and power levels. This amplifier can’t output signals above 35w.

It can be powered with mains supply and also with battery. Battery power is used when there is no mains power supply and the battery charges when mains is at work.

1.6                                        PROJECT WORK ORGANIZATION

The various stages involved in the development of this project have been properly put into five chapters to enhance comprehensive and concise reading. In this project thesis, the project is organized sequentially as follows:

Chapter one of this work is on the introduction to an audio stereo amplifier. In this chapter, the background, significance, objective limitation and problem of an audio stereo amplifier were discussed.

Chapter two is on literature review of  an audio stereo amplifier. In this chapter, all the literature pertaining to this work was reviewed.

Chapter three is on design methodology. In this chapter all the method involved during the design and construction were discussed.

Chapter four is on testing analysis. All testing that result accurate functionality was analyzed.

Chapter five is on conclusion, recommendation and references.